The present invention relates to an improved pneumatic governor control apparatus for an engine fuel injection system.
It is common to provide Diesel engines with fuel injection systems which are controlled by pneumatic governors. The governor is connected to a venturi which is provided upstream of the engine intake manifold in the air induction passageway. The vacuum in the venturi is applied to a diaphragm in the governor which controls the amount of fuel injected into the engine by a fuel injection pump in accordance with the level of vacuum.
In addition to generally inaccurate fuel injection control, such an arrangement suffers from several serious drawbacks.
1. The venturi constricts the air induction passageway during high load, high speed engine operation to such an extent as to degrade the air induction efficiency and engine output power.
2. Whereas in a gasoline engine provided with an electric ignition system, the engine may be easily shut off by merely de-energizing the ignition system, in a Diesel engine either the fuel or air supply must be shut off. This is because the engine automatically draws fuel and air into the induction passageway as a consequence of operation. It is therefore relatively difficult to stop a Diesel engine quickly.
3. Where exhaust gas recirculation is incorporated to reduce the emission of pollutants, variations of pressure in the intake manifold make it difficult to accurately sense the exhaust gas pressure which varies in accordance with engine load.